This invention relates to a process for forming a light-reflecting bar code on end disc of photographic film spool.
In a known photographic film patrone of APS (i.e., Advanced Photo System), a light-reflecting bar code is generally provided on an end disc (or flange) which is attached to an end of the spool. The light-reflecting bar code gives encoded film data such as film sensitivity and the number of exposed frames, and thereby the film data can be photoelectrically recognized. The light-reflecting bar code can be formed, for example, by the process disclosed in Japanese Patent Provisional Publication No. 8-254794. In the disclosed process, a hot-stamp film having a light-reflecting metal layer such as aluminum foil is pressed onto an end disc of spool by a stamping die having the bar code on its surface, so as to transfer the light-reflecting metal layer onto the end disc in the pattern of the bar code.
Japanese Patent Provisional Publication Nos. 9-14622 and 11-133552 disclose a hot-stamping process and a hot-stamping apparatus for industrially and advantageously forming light-reflecting bar codes on an end disc of spool. The hot-stamping apparatus disclosed in Japanese Patent Provisional Publication No. 9-14622 is shown in the attached FIG. 2. In FIG. 2, the hot-stamping apparatus 20 comprises a fixed holder 21, a movable holder 24 which can move along the direction of arrow, and a stamper (i.e., bar code pattern transfer die) 27 by which a hot-stamp film 10 is pressed onto an end disc of spool. In the apparatus 20, the spool 28 is made to stand in the fixed holder 21 with a tenon 22 and a supporting wall 23 so that the end disc 29 may be placed on the top. The spool 28 standing in the fixed holder 21 is then passed to a fork claw 25 provided on the movable holder 24. The fork claw 25 has an independent cushion member 26, and the cushion member 26 gives constant even force with which the stamper 27 presses the hot-stamp film 10 onto the end disc 29 of the spool 28. (Hereinafter, this force is referred to as xe2x80x9cstamping forcexe2x80x9d.) Thus, by means of the hot-stamping apparatus, a light-reflecting bar code can be formed on the end disc. In the process with the hot-stamping apparatus described above, bar code pattern-transferring troubles such as missing foil or forming fins at the foil edge can be avoided. Further, the disclosed bar code pattern-transferring process is also described to give plural light-reflecting bar codes in a relatively short time.
The applicants have noticed that transferring troubles often occurs when plural light-reflecting bar codes are successively formed on end discs of spools by means of the aforementioned apparatus. In fact, if one stamper is used in the transferring process to form 3,000 to 4,000 light-reflecting bar code patterns on end discs of the corresponding number, transferring troubles remarkably increase (troubles arise twice or more as frequently as those at the beginning). The applicants have studied this problem, and found that stains deposited on the stamper make the stamper surface uneven to cause the troubles. When a light-reflecting bar code is formed in the transferring process (i.e., when the stamper presses a hot-stamp film onto an end disc), the die surface of the stamper is stained. Accordingly, after 3,000 to 4,000 light-reflecting bar codes are formed on end discs (i.e., after the transferring process is repeated 3,000 to 4,000 times), accumulated stains make the die surface uneven and hence make stamping force so uneven as to cause the troubles.
Although the stains on the die surface of the stamper can be removed by washing, the process must be discontinued when the die surface is washed or exchanged. Consequently, the efficiency for producing light-reflecting bar code patterns is considerably impaired.
Accordingly; it is an object of the present invention to provide a process for efficiently forming light-reflecting bar code patterns on end discs of photographic film spools. In the process of the invention, the surface of die surface of the stamper is hardly stained.
The applicants have studied to achieve the object, and finally found that the stains on the-die surface of stamper can be avoided by a hot-stamp film having a stain-shielding layer provided on the face to be brought into contact with the die surface.
The present invention resides in a process for forming a light-reflecting bar code on an end disc of photographic film spool, comprising the steps of:
placing on the end disc of photographic film spool a hot-stamp film comprising, in order, an adhesive layer, a light-reflecting metal layer, a transparent protective layer, a releasing layer, a support film, and a stain-shielding layer formed of material inhibiting migration of a compound having a low molecular weight from the support film in such manner that the adhesive layer is brought into contact with the end disc and
pressing for a period of 0.1 to 2.0 seconds a stamper which has a bar code-stamping die heated to 150 to 200xc2x0 C. so as to transfer the light-reflecting metal layer onto the end disc in the form of the bar code.
The support film of the hot-stamp film is preferably made of polyester resin, and the material inhibiting migration of a compound having a low molecular weight from the support film preferably is a compound having a siloxane bonding or deposited inorganic oxide.